Slip ring assembly and process of manufacturing same



March 25, 1969 H, SMWH 3,435,402

SLIP RING ASSEMBLY AND PROCESS OF MANUFACTURING SAME Filed Harsh 30, 1966 Sheet of 2 I r 1% -a\ \lfiliQ lpklkll v 11mm] 1| 1 #mnm.immmmfi1IHIIQHIifl'liljillf'l iillillf 1' i I) I2 3 .FzyJU INVENTOR Fifi/4N5 544/777 B FEM A TQRNEY- V H. E. SMITH March 25, 1969 SLIP RING ASSEMBLY AND PROCESS OF MANUFACTURING SAME Sheet Filed March 30, 1966 STAMPING LAYOUT PRIOR ART STAMPING LAYOUT I N V E N TO 2 HEPMAA E 524/777 ATTORNEY United States Patent 3,435,402 SLIP RING ASSEMBLY AND PROCESS OF MANUFACTURING SAME Herman E. Smith, Park Forest, 111., assignor to Borg- Warner Corporation, Chicago, 111., a corporation of Illinois Filed Mar. 30, 1966, Ser. No. 538,769 Int. Cl. H01: 39/00, 9/08, 43/00 US. Cl. 339- 2 Claims ABSTRACT OF THE DISCLOSURE This invention relates to current collecting and distributing devices and, more particularly, to slip ring assemblies.

Slip ring assemblies normally include a non-conductive cylindrical core member having a plurality of spaced apart eircumferentially extending conductive rings disposed on the exterior thereof. Each of the conductive rings is provided with an electrical lead which may be formed as an integral part of the ring. The lead normally extends through at least a part of the cylindrical core member.

Slip ring assemblies have been manufactured by stamping an elongated generally rectangular flat strip of conductive material from a blank, forming the strip into an annular configuration, molding a central non-conductive core member within the annular member and subsequently removing narrow sections from the strip thus forming circumferentially extending grooves in the strip to define and isolate certain sections of the flat strip from each other and thus form a plurality of spaced apart circumferentially extending rings. Integral leads, oriented laterally with respect to the rectangular strip, have been formed as part of the initial stamping operation. These leads have been formed into their final configuration during the step wherein the strip is formed into the aforementioned annular configuration. Each lead thus extends radially inwardly with respect to its respective ring and extends axially through the central core member to a point laterally of the outer slip ring. A more detailed description of this method of making a slip ring assembly with integral leads is set forth in United States Patent No. 3,253,325, issued May 31, 1966, entitled, Method of Making a Slip Ring.

One of thep roblems encountered in the manufacture of slip ring assemblies in accordance with the method described above, is the waste of blank material resulting from the stamping operation. This is due, at least in part, to the fact that only a small amount of the material adjacent the elongated dimension of the rectangular strip is utilized to form the leads. Thus, at best, the material adjacent the elongated dimension can be used to form leads for two rectangular strips.

It is, therefore, an object of this invention to provide a means of stamping an elongated strip of material which may then be formed into an annular configuration and integral leads formed with respect to each of the conductive strips whereby the amount of waste or scrap material associated with the stamping operation is minimized and/ or eliminated.

Briefly described, this invention relates to the manufacture of a slip ring assembly wherein the elongated strip 3,435,402 Patented Mar. 25, 1969 member used therein is formed from a blank such that it includes a plurality of ring portions and integral lead portions for each ring portion, which lead portions are aligned longitudinally with respect to the elongated dimension ring portions. This is in contradistinction to the lateral orienta tion of the lead portion with respect to the ring portion as taught in the above mentioned prior art. The elongated strip member of the present invention is further particularly characterized as having each ring and lead portion displaced longitudinally with respect to the next adjacent ring and lead portion. The amount each ring and lead portion is displaced with respect to the adjacent ring and lead portion depends on the particular desired structure; however, at a minimum, the amount preferably equals the length of the lead portion.

Other features, objects, and advantages of the invention will apepar from the following detailed description of a preferred embodiment of the invention, in which:

FIGURE 1 is a perspective view of the conductive elongated strip member during one stage of fabrication of the slip ring assembly;

FIGURE 2 is a view taken generally along section lines 2-2 of FIGURE 1;

FIGURE 3 is a partial perspective view of the integral lead portion of the conductive strip member and its associated ring member during one stage of fabrication of the slip ring assembly;

FIGURE 4 is a perspective view of an alternate embodiment of the strip member during one stage of fabrication of the slip ring assembly;

FIGURE 5 is a view taken generally along section lines 5'-5 of FIGURE 4;

FIGURE 6 is a partial perspective view of an alternate embodiment of an integral lead portion of the strip member and its associated ring member during one stage of fabrication of the slip ring assembly;

FIGURE 7 is a partial perspective view of the ring portion illustrating the anchoring means;

FIGURE 8 is a partial perspective view of an alternate embodiment of the anchoring means illustrated in FIGURE 7;

FIGURE 9 is a partial cross-sectional view of the anchoring means of a ring and its interlocking relationship with the interior core member;

FIGURE 10 is a plan view of the inwardly facing surface of a conductive strip of material which is used to fabricate the slip ring assembly;

FIGURE 11 is a view of a typical stamping layout used in conjunction with making a slip ring assembly as taught in the present invention;

FIGURE 12 is a view of a typical stamping layout used in conjunction with making a slip ring assembly as taught in the prior art; and

FIGURE 13 is a perspective view, partially in section, of a slip ring assembly of the present invention.

Referring now to the drawings and, more particularly, FIGURE 10, a strip of conductive material 20 is preferably formed from a larger blank of material by a conventional stamping operation such that it is of a generally elongated configuration. It, as illustrated, includes three distinct ring sections, r r and r and three distinct lead sections, l l and The stamping operation includes a shearing operation resulting in a lengthwise slit 12 between L and L and a similar slit 14 between L and L3.

The inwardly facing surface Fof the strip 20 may include means for anchoring the strip to the interior core member 30. In the illustrated embodiment, this means includes longitudinally extending ribs 22 which are of a generally dove-tail shaped cross-sectional configuration (FIGURES 7, 8 and 9). Grooves 24, which are located between the ribs 22, may include transversely extending 3 raised portions 26 (FIGURE 7) and/or transversely extending depressions 28 (FIGURE 8).

Centrifugal forces associated with rotation of a slip ring assembly tend to separate the rings from the core member. The dove-tailed configuration of ribs 22 provides a means to interlock the ring and the interior core member (see FIGURE 9) and thus minimizes the destructive effect of centrifugal force as the assembly rotates. Additionally, the ribs 22 restrict axial movement of each ring with respect to the central core member. The raised portions 26 in the bottom of the grooves 24 (FIGURE 7) and/ or the depressions 28 in the bottom of the grooves 24 (FIGURE 8) provide an additional interlocking means which restricts relative circumferential movement of the ring with respect to the core member. The method of forming the anchoring means on the interior surface of the conductive strip material 20 is described in detail in United States Patent No. 3,253,325.

After the step of stamping the strip 20 from a blank, the strip is preferably formed into an annular configuration such that opposite ends of each ring section, r r and r are juxtaposed. Each lead, l l and I is formed with a radially inwardly extending section i and an axially extending section x. Each lead is of a length sufiicient to extend exteriorly of the ring assembly (FIG- URES 1, 2, 4 and 5).

After the conductive strip has been formed into an annular configuration as illustrated in FIGURES 1 and 4, a central core member 30 is poured or molded into the interior portion thereof. The core member may be formed from a non-conductive material which is capable of flowing into the annular assembly and thereafter sets to form a strong core body. An example of a material suitable for use as the core material is a thermo-setting phenolic resin which may include filler material.

After the formation of the core 30, circumferentially extending sections are removed from the strip 20* to form grooves 32. This separates the individual rings, r r and r from each other.

The leads l l and 1 of the embodiment illustrated in FIGURES 1-3 extend from their respective rings, r r and r through two [generally 90 bends such that the major dimension of the body portion of the lead is oriented circumferentially with respect to the rotational axis of the slip ring assembly. The configuration of leads l and 1 in the alternate embodiment illustrated in FIGURES 4-6 differs from the configuration illustrated in FIGURES 1-3 in that the alternate embodiment illustrates more severe or tighter bend in each lead such that the major dimension of the body portion of the lead is oriented radially with respect to the rotational axis of the slip ring assembly.

A comparison of FIGURE 11 with FIGURE 12 illustnates the relative difference in the stamping layout utilizing the teaching of the present invention and that of the prior art. The stamping layout utilized in the present invention (FIGURE 11) results in a repetitive pattern wherein very little, if any, Waste is associated with the stamping operation. FIGURE 12 illustrates a stamp ing layout wherein laterally oriented leads are formed integral with each ring portion. In this prior art method of stamping the assembly, the pattern requires each ring section be longitudinally offset with respect to its adjacent ring section such that the laterally extending leads 4 can be formed integral with their respective ring portions. This requirement, therefore, results in a pattern as illustrated in FIGURE 12 wherein portions of the blank adjacent the side edge of the assembly and portions between the ends of the successive patterns must be Wasted. The waste area is illustrated in FIGURE 12 by hatch lines.

While a certain preferred embodiment of the invention has been specifically disclosed, it is understood that the invention is not limited thereto, as many variations will be readily apparent to those skilled in the art and the invention is to be given its broadest possible interpretation within the terms of the following claims.

What is claimed is:

1. A slip ring assembly comprising a cylindrical insulating core member, a plurality of elongated spaced apart conductive rings disposed on the periphery of said insulating core member, said elongated spaced apart conductive rings having juxtaposed end portions, a lead for each of said elongated spaced apart conductive rings, said leads having oppositely disposed lead end portions, said leads extending from saind rings radially inwardly within and axially through said core member such that one lead end portion is adapted to be connected to an electrical conductor, each lead including one lead end portion coextensive with and integral with one ring end portion.

2. A process for manufacturing a slip ring, the steps comprising:

stamping an elongated strip of conductive material from a blank such that the strip includes a plurality of elongated ring portions extending in a longitudinal direction with respect to said strip, each ring portion being progressively longitudinally displaced from its next adjacent ring portion, and a plurality of lead portions each extending longitudinally from one end of each ring portion;

forming said strip into an annular configuration such that the ends of each said ring portion abut and such that each said lead portion extends radially inwardly and such that the terminal end of each said lead portion extends transverse its original longitudinal orientation with respect to said ring portion;

forming a central core member of non-conductive material within the interior portion of said annular strip; and

removing from the peripheral portion of said strip a plurality of circumferentially-extending sections to a depth sufiicient to separate said rings one from another.

References Cited UNITED STATES PATENTS 1,493,859 5/1924 Hirnes 339-5 3,289,140 11/1966 Slack 3395 FOREIGN PATENTS 940,370 5/ 1948 France.

RICHARD E. MOORE, Primary Examiner.

US. Cl. X.R. 

